The invention relates to lathes, and more particularly, to a mechanical-hydraulic radial feed system for a lathe having a plurality of tools which can be selectively operated in the radial direction to cut a workpiece in the form of wire or rod which is carried by a headstock for rotation and axial movement therewith.
In known lathes there are provided a plurality of tool slides capable of movement in the radial direction of the workpiece and which are operated by corresponding profile cams mounted on a common control shaft and which in turn act through strongly spring biased lever mechanisms. In automatic lathes, lever mechanisms having different lengths constitute the path for transmission of force from the associated cams to the respective tool slides, so that the transmission loss resulting from the rigidity of levers and the joint between the levers as well as the relative magnitude of such loss are of a great consequence. An automatic lathe having an increased length of the transmission path is inadequate for a high precision machining, and additionally presents inconveniences because of varying machining precision associated with different tool slides. The preparation of a plurality of cams applicable to the respective tool slides and their positioning in predetermined orientations on the common control shaft also represent a troublesome operation.
The above described disadvantages can be overcome in part by driving the tool slides with corresponding hydraulic cylinder units. A construction of this type is disclosed in Japanese Patent Publication No. 15,356/1970 which is based on its counterpart application in West Germany filed Dec. 21, 1965. In the disclosed arrangement, each tool slide is connected with a piston rod of an associated hydraulic cylinder unit, so that the path of transmission mentioned above can be minimized. However, the motion of the tool slides is controlled by a switching of control valves which are connected between the cylinder units and a pump. As a result, in contrast to the forced drive transmitted through the lever mechanisms mentioned above, alignment with the cams is not assured. In addition, a variation in the consistency of the working fluid resulting from temperature changes gives rise to a deviation, requiring resort to a manual adjustment of screw stops in determining the amount of feed.